Energy band alignment in GaAs:(Al,Ga)As heterostructures: The dependence on alloy composition

Abstract

The band alignment in GaAs:(Al,Ga)As heterostructures has been investigated over the full range of alloy composition. The valence-band discontinuity ΔEv is determined by measuring the activation energy for thermionic emission of holes from p-GaAs over an undoped, square (Al,Ga)As barrier. The use of p-type structures to measure ΔEv circumvents a number of complications involved in the measurement of ΔEc. The parameters required for analysis are determined by different measurements on the same structures and the analysis is performed so that the activation energy, extrapolated to zero bias, yields ΔEv directly. It is found that ΔEv is a linear function of the aluminum mole fraction xAl: ΔEv ≂0.55xAl (eV) (0≤xAl≤1). The validity of these data is supported by measurements of ΔEc in the direct band-gap regime, where complementary values of ΔEv and ΔEc add up to the expected band-gap difference. This relationship provides a simple description of the full band alignment in this heterosystem and should prove valuable as a test of the various heterojunction lineup theories. Moreover, these measurements have a number of important consequences, particularly from the viewpoint of heterojunction devices.

Band offset of GaAs/AlxGa1−xAs heterojunctions from atomistic first principles

“…Near and beyond the direct gap range, the calculated CBO decreases with increasing of x, which is also in good agreement with the experimental results. 3 …”

“…For many III-V materials systems, the band offset has been carefully measured experimentally. 2,3 Theoretical calculations of band offset have always been a serious challenge. This is because first principles method of density function theory (DFT) with local-density approximation (LDA) 4 and generalized gradient approximation (GGA) 5 underestimates the band gap (E g ) of semiconductors.…”

Analytical expressions for asymmetric double quantum wells and their application to semiconductor heterostructures

“…A large number of reports are available on effective mass and conduction band offset variations with respect to composition parameter X [23][24][25][26][27]. We have taken the following dependences from [23]:…”

Resonance condition for asymmetrical triple-barrier structures

“…It is assumed that the conduction-band offset at the heterojunction interfaces between Ga 0.7 Al 0.3 As and GaAs is 0.3 eV, and the conduction-band offset between GaAs and AlAs 1.0 eV [24].…”